15:30-16:30
Phase Transitions, Atom Diffusion and Adatom-Adatom Interactions on Surfaces:Variable Temperature STM Studies
Prof.Jose M.Gomez-Rodriguez(Departamento de Fisica de la Materia Condensada Universidad Autonoma de Madrid Madrid, Spain)
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Low-dimensional systems are an ideal playground for the analysis of critical phenomena. In particular, structural phase transitions taking place at surfaces have been the subject of intense experimental and theoretical research for the last few decades. The development of new experimental techniques such as variable temperature scanning tunneling microscopy (VT-STM) has widened, much more recently, our view of the microscopic aspects of some of such transitions. In this talk, first, it will be presented an example of the application of VT-STM to the analysis of phase transitions taking place on reconstructed surfaces formed by the adsorption of metallic atoms on semiconductor substrates. In particular, it will be shown how VT-STM can provide valuable information on the (√3x√3)R30°⇔(3x3) phase transition that takes place on the Pb/Si(111) system at low temperature (1,2). Second, it will be shown a VT-STM study of the diffusion of single additional adatoms deposited at low temperature on these surfaces (3) and the influence that the existence of an structural phase transition at lower temperatures can have on this process. In particular, it will be shown in the last part of this talk the existence of a new kind of adatom-adatom substrate-mediated interaction (4) that is related to the phase transition and can be detected even at temperatures higher than the critical temperature.
(1)I. Brihuega, O. Custance, R. Perez, and J.M. Gomez-Rodriguez, Phys. Rev. Lett. 94, 046101 (2005).
(2) I. Brihuega, O. Custance, M.M. Ugeda, N. Oyabu, S. Morita, and J.M. Gomez-Rodriguez, Phys. Rev. Lett. 95, 206102 (2005).
(3) I. Brihuega, M. M. Ugeda, and J. M. Gomez-Rodriguez, Phys. Rev. B 76, 035422 (2007).
(4) I. Brihuega, A. Cano, M.M. Ugeda, J.J. Saenz, A.P. Levanyuk, and J.M. Gomez-Rodriguez, Phys. Rev. Lett. 98, 156102 (2007).